1. Field of the Invention
This invention relates to a method and an apparatus for extracting packing rings from a stuffing-box, for example in a pump, a compressor or a valve.
2. Description of the Prior Art
A stuffing-box, commonly used to ensure fluid-tightness around the movable stem of a device such as a pump, a compressor or a valve, typically comprises several annular slotted packing rings fitted around the movable stem and contained in a box integral with the device, the packing rings being maintained under compression in the box by a follower or gland mounted on a flange which is bolted down towards a plate solid with the box.
After a working period which can be relatively short when the device is used with high pressure or high temperature fluids, it is necessary to replace the packing rings in order to maintain a satisfactory fluid-tightness. To achieve this, one unbolts the flange from the plate and raises the latter along the stem so as to be able to extract the follower from the box and gain access to the packing rings.
Up to now, these packing rings were successively hand extracted with the help of hooks or "corkscrew" type tools such as the extractor described in U.S. Pat. No. 3,861,248, which were driven in the upper packing and then raised in order to pull the latter out of the box.
Yet, the packing rings squeezed in the box by the follower during the working of the device have a very hard surface and are often jammed in the box. Under these conditions it is difficult for the hook to engage a packing ring and sometimes requires the use of large mechanical forces which might damage the stuffing-box or stem of the device; furthermore in some instances the follower cannot be sufficiently moved away from the box without completely dismantling the device, which renders the access to the packing rings difficult and sometimes even almost impossible.
In the worst cases the extraction operation may last several hours, which is always a significant drawback and becomes unacceptable when the operator must work in a polluted environment, as for example in nuclear power stations.